code: def test_fixed_lambda(self):
      mixup = Mixup(-0.1, 0.3)
      X = torch.Tensor([[1.0, 2.0, 3.0], [6.0, 7.0, 8.0]])
      Y_true = torch.Tensor([0.0, 1.0])
      lam = 0.3
  
      state = {
          torchbearer.X: X,
          torchbearer.Y_TRUE: Y_true,
          torchbearer.MIXUP_LAMBDA: lam,
      }
  
      mixup.on_sample(state)
      self.assertTrue(
          state[torchbearer.X][0][1] == 0.3 * 2 + 0.7 * 2
          or state[torchbearer.X][0][1] == 0.3 * 2 + 0.7 * 7
      )
  
file_path: torchbearer/tests/callbacks/test_mixup.py
imports: from unittest import TestCase
  from mock import patch, call, MagicMock
  import torch
  import torchbearer
  from torchbearer.callbacks import Mixup, MixupAcc
label_desc: Use image node_id 3 for calling the TestMixupInputs obj's underlying member method code with example usage: obj.test_fixed_lambda() without return types